“Assessing the contributions of reduced immigrant viability and fecundity to reproductive isolation”

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Cody K. Porter and Craig W. Benkman

Reduced immigrant fecundity is a stronger driver of speciation than reduced immigrant viability

As populations adapt to different environments, opportunities for interbreeding decline if immigrants suffer reduced fitness in their non-native environment. Although such a reproductive isolating barrier could arise from reduced immigrant survival or reduced immigrant fecundity, the former (immigrant inviability) has received the vast majority of study. However, given the often greater resource demands for breeding than for survival, one might expect that reduced immigrant fecundity could act as the stronger reproductive isolating barrier. In a paper appearing in The American Naturalist, a model simulates the evolution of reproductive isolation as populations adapt to different environments, taking into account the greater resource demands of reproduction than for survival alone. This model, along with analyses of published reciprocal transplant experiments, indicate that reduced immigrant fecundity is likely to act as the stronger reproductive isolating barrier, especially when the demands of reproduction are relatively large and during the initial stages of divergence. These results suggest that reduced immigrant fecundity deserves greater attention if we are to understand the important reproductive isolating barriers during the critical early stages of speciation. Read the Article